Last year, thousands of children in China died in the Sichuan earthquake when their poorly constructed schools collapsed, even as government and private structures remained standing. The tragedy brought scrutiny to schools located in quake-prone communities around the United States, including Portland, which the Federal Emergency Management Agency ranks among the top forty cities most at risk for an earthquake.
Portlanders live the Cascadia subduction zone, a volatile seven-hundred-mile region along the Oregon Coast that also includes Northern California, Washington, and southern British Columbia. This zone hasn’t produced an earthquake in hundreds of years, but the US Geological Survey puts the likelihood of a quake in the next thirty years at 10 percent, and they expect it to be thirty-two times stronger than the one in China. Portland’s bridges will fall, structures will crumble, the granite and marble façades of downtown buildings will rain to the streets. The shaking will last not for seconds but for long minutes. Late next month, state Department of Emergency Management authorities will stage an earthquake drill on the educated premise of 750 people dead, 13,000 injured, and 23,000 in need of shelter—in Multnomah County alone.
When the real thing hits, schools will be especially vulnerable. A 2007 study by the state Department of Geology and Mineral Industries (DOGAMI) placed 1,018 of the 2,185 Oregon school buildings studied at a “high or very high risk” of collapse.
Yumei Wang, a geotechnical engineer and a national expert on earthquake mitigation and risk assessment, leads Oregon’s geohazards team for the Portland office of the DOGAMI. She participated in the 2007 schools analysis. We spoke with Wang about the massive quake coming our way, our woeful lack of preparedness, and why 2009 may be a watershed year for retrofitting schools with the kinds of materials that might save lives.
*_Portland Monthly_ : First of all, why will this earthquake that scientists are predicting be so huge?
Yumei Wang: Different kinds of earthquakes have different maximum capacity. About fifty miles off the Oregon Coast, there is a plate tectonic boundary that affects Northern California, Oregon, Washington, and part of British Columbia. An oceanic plate is being shoved underneath the Continental North American Plate. This is called the Cascadia subduction zone. We know from empirical data that subduction zone earthquakes produce the largest earthquakes in the world. The best known recent subduction quake is the 2004 Indian Ocean quake, magnitude 9.1.
PM: The geological record shows that Cascadia subduction zone quakes occur about every three hundred to eight hundred years. The last one occurred in 1700. Are we due?
Wang: This is an earthquake that will definitely occur. It’s like death and taxes—it’s gonna happen. We just don’t know when.
PM: How much shaking actually occurs during a magnitude 9 earthquake?
Wang: During the Indian Ocean quake, there were ten minutes of strong ground-shaking during the rupture, and those waves traveled out and continued to shake more in some areas than others. That area has also been plagued with major earthquakes, above a magnitude 8, since the original rupture. It’s the same subduction zone; the quake has just been traveling up and down.
PM: How would a major quake transform our landscape?
Wang: All of Portland is going to be shaken hard—that’s one thing I want to make sure is understood. There is going to be damage in some areas more than others. In the West Hills, we can expect to have earthquake-triggered landslides—we could have hundreds of landslides in the Portland Hills during a major quake. We would expect to have extensive liquefaction, where the ground turns temporarily into a sandy liquid along the Willamette and Columbia Rivers. So if you think of all the industry and development that we have there, those are going to be in trouble. You have petroleum tank farms, rail yards that are a vital part of our transportation; our fuel pipelines are there; our electrical transmissions cross in North and Northwest Portland. There’s also the airport and the levies that are vital to the airport. In areas like Old Town, which has very vulnerable buildings and where there is a concentration of older, unreinforced masonry buildings, we expect to have a lot of severe damage.